1. Field of the Invention
The invention relates to vehicular lamp including a cut-off forming member.
2. Description of Related Art
Typically, a projector type vehicular lamp forms a light distribution pattern by invertedly projecting a light source image formed on a rear side focal plane of a projection lens forward.
Also, when forming a light distribution pattern having a cut-off line at an upper end portion, such as a low-beam distribution pattern, by radiated light from such a vehicular lamp, a cut-off forming member such as a shade is arranged between a light source and a projection lens.
Japanese Patent Application Publication No. 2003-338209 (JP 2003-338209 A) describes such a projection type vehicular lamp having a configuration in which a first sub-reflector that reflects light from a light source downward, and a second sub-reflector that reflects the reflected light from this first sub-reflector forward so that it passes through a lower space of the projection lens, are both arranged in front of a reflector that reflects light from the light source toward a projection lens.
Meanwhile, Japanese Patent Application Publication No. 2012-190551 (JP 2012-190551 A) describes such a projection type vehicular lamp having a configuration in which a sub-reflector that retroreflects light from a light source so that it returns to the position of the light source is arranged in front of a reflector that reflects light from the light source toward a projection lens. In this vehicular lamp, the retroreflected light from the sub-reflector is reflected by a surface of the light source (more specifically, a light-emitting device) so that it strikes the reflector again, and this reflected light from the reflector is re-reflected toward the projection lens.
By employing the lamp configuration described in JP 2003-338209 A, an additional light distribution pattern formed by the light from the light source that has been sequentially reflected by the first and second sub-reflectors is added to the light distribution pattern formed by emitted light from the projection lens, thereby enabling the brightness of the light distribution pattern to be reinforced.
However, when this kind of configuration is employed, the size in the vertical direction of the overall lamp ends up increasing due to the presence of the first and second sub-reflectors, so the lamp may not be able to be made compact.
On the other hand, by employing the lamp configuration described in JP 2012-190551 A, the brightness of the light distribution pattern is able to be reinforced while making the lamp compact.
However, when this kind of configuration is employed, the retroreflected light from the sub-reflector is first reflected by the surface of the light source, and then re-reflected by the reflector, so the degree of freedom in the formation position and shape of the additional light distribution pattern formed by this re-reflected light decreases. Therefore, it is difficult to effectively reinforce the brightness of the light distribution pattern.